I am trying to simulate the behavior of helical anchors (also called screw anchors) using PLAXIS 3D and a clay hypoplasticity constitutive model. The helical anchor shaft is simulated as a half cylinder volume element (to obtain moments and forces in a convenient way), covered by a low stiffness plate element at its curved surface. Helical plates (simulated as planar plate-type elements) are attached perpendicularly to the preceding plate. A positive interface is added to the shaft plate while positive and negative interfaces are added to the “helical” plates.

Vertical and lateral forces are applied to the head of the anchor in a displacement-controlled test. The calculation procedure is performed with the Picos solver with the arc-length method setting turned off. Also, I have changed the maximum load fraction step for smaller steps to the program default.

I am experiencing difficulty while loading this element in either direction as the interface experiences excessive deformations followed by a dropdown in the load-displacement plot, no matter the interface resistance parameters.

Based on some requests, I share here two presentations on hypoplasticity applications. One is related to simulation of various boundary value problems, the other focuses on simulation of cyclic and […]

Our article published in the latest issue of Ground Engineering 10/2017. Great combination of cone-pressueremeter-testing (CPM) by FUGRO and advanced 3D Fem modelling by GEOLINK using hypoplastic constitutive equations to […]

The 2014 Masin hypoplasticity for clays has been implemented in Tochnog Professional under guidance of Dr. David Masin. This implementation includes structure, intergranular strains and visco effects. Extensions to the […]

The equations for a vertical cut in cohesive material are given in several publications including Heyman (1973): The stability of a vertical cut (see attachment Equations1.jpeg) and Verruijt (2001) Soil […]

The Tochnog Professional finite element program is now available as free version with 100 elements. It can be downloaded without registration from http://www.feat.nl. Several commercial and free pre- and postprocessors […]

The interface was hypoplastic (the parameters were defined from the adjacent soil). After I posted this question I tried to run the model with Hardening Soil, and the same issue was present. I created a new Mohr-Coulomb material and assigned this to the interface and it seems to work. I wonder what happens when the interface has the same model than the adjacent soil.

Another question that I have right now is how to reduce the computational time when performing a large displacement calculation. I am waiting for Plaxis support with this issue, but, is there any recommendation I might address.

Hi Leon,
Considering that the problem persists with Hadening soil model, this means that the problem is not related to hypoplasticity and in its implementation. There may be various reasons then which are hard to investigate by this simple communication. I suggest that you try to work-out the problem with Plaxis support while using HardeningSoil model, once resolved, you can switch back to hypoplasticity and I believe the model will work.
Regards David